Yes; used to occasionally fly BOS-Manchester, UK on AA's 757 (mid 2000s) for work before they cancelled that service. It wasn't horrible, but when compared to AA's 777 BOS-LHR at the same time, there was no comparison. First, no matter how good the service is, having only one aisle for people to try to go to the bathroom is problematic on long flights. But even worse than the 1 aisle is the total lack of congregating space...it'd be one thing if they removed a row or two of seats near the facilities (which AA did not do with the 757 at the time). I understand on regional flights they ask you not to stand around, but on a 6hr flight, it's kind of unreasonable to ask all 180+ people not to move.
My general sense is that I would have given the coach experience on the BOS-LHR widebody an A- at the time, and the 757 experience a B- in the same timeframe. The difference was not enough for me to prefer a connecting flight arrangement to MAN - it was still worth getting to my destination non-stop. But one simply can't say its the same product. To AA's credit though, I'll say that the meal service/FA competence was generally equivalent to their widebody service. They seemed to use legit international-trained FAs despite the narrowbody.
So I think to fully answer your question about whether narrowbody is OK, you'd have to find out about the seating arrangement (any open space added?) and FA capabilities/level of service.
Just my 2 cents.